1. Field of the Invention.
The present invention relates generally to a device for detecting and measuring the magnitude of an externally generated current passing radially through a planar metallic conductor that radially terminates a coaxial-conductor-configured sense line and, more particularly, to such a device capable of detecting and measuring electric current over an extended frequency range.
2. Description of the Related Art.
The detection and measurement of electric currents through application of the general principle of induction is well known, as exemplified by clamp-on magnetic loops with inductively coupled coils of wire used to measure the alternating magnetic field of the current. The wire loops generally limit the use to about 100,000,000 Hertz (100 MHz). The clamp-on probe is not applicable in a coaxial circuit where low reflection is required.
Conventionally, the detection of voltage is commonly achieved through a high value resistor for isolation which is subject to capacitive coupling errors at frequencies of about 100 MHz or above. Modern amplifiers are so output-load-tolerant that often a matching load is not utilized. This results in high currents into essentially shorted test setups, thus making a voltage probe not applicable.
Discrete resistive elements in various series/parallel combinations having special configurations are utilized to detect electrical signals, such as electrostatic discharge (ESD), but these also exhibit inductive and capacitive effects that distort the signal and provide misleading test information near gigahertz (10.sup.9 Hertz) frequencies.
The use of a resistive foil, current detecting device, inserted as part of the ground shield return path of a coaxial connector (described in U.S. Pat. No. 4,804,917 of John S. Miller, one of the inventors herein) is possible through utilization of a coaxial configuration that essentially eliminates capacitive and inductive pickup and therefore is mostly pure resistance, even at fractional ohmic levels and at frequencies higher than 1 gigahertz. Another current detection device utilizing thin resistive foil laid down on the outer surface of an annular dielectric substrate is disclosed in U.S. Pat. No. 4,719,414 of John S. Miller et al.
It is, therefore, a primary object and aim of the present invention to provide a coaxial termination, current detection device capable of achieving an exceptionally wide range of frequency response, namely, D.C. to 10 gigahertz.
Another object is to provide such a current detection device incorporated into a test arrangement for detecting and measuring electrical discharge onto a container that is, or simulates, the equipment to be tested. One example would be a test method for identifying the electrostatic discharge susceptibility of electronic equipment utilizing the device to identify the imparted current waveshape to assure meeting the requirements of applicable technical standards at various test locations.